Wiktionary
n. A diet consisting of foods from all food groups.
WordNet
n. a diet that contains adequate amounts of all the necessary nutrients required for healthy growth and activity
Usage examples of "balanced diet".
She ate a healthy, well-balanced diet, and didn't think about food all that much.
Apparently, prairie folk have little concern for a balanced diet, because no fresh fruits or vegetables seem to be sold here, only a variety of packaged goods.
Cereals and pulses together thus provide many of the ingredients of a balanced diet.
I know you hunter types would prefer to go for the meat but these can be just as important to a properly balanced diet.
The foods were nonperishable and constituted a more-or-less-balanced diet.
When she did eat, she touched only nutritious food, a more well balanced diet than at any time in her life.